Roberta (r) says she and her colleagues are as stubborn as the fiercest bug

Trauma nurse Roberta Gately, who works for the International Rescue Committee aid agency, tells BBC News Online about trying to help some of the 1.5 million people who have fled their homes in Sudan's war-torn region of Darfur.

The people of Darfur, who live in one of the poorest and most inaccessible regions in the world, are accustomed to deprivation and misery. But not on the scale that now consumes them.

Forced to flee their homes, they are living in crowded, squalid camps, dependent on numerous agencies for food, shelter, medical care, even for hope.

Many only narrowly escaped with their lives and now they face deadly epidemics which thrive in crowded refugee settings.

Of all the diseases for which there is a vaccine, measles is the leading cause of death among displaced children worldwide due to their already precarious state of health.

Desperate conditions

One recent outbreak killed 23 children at Abu Shouk camp in North Darfur. The spread of measles in a refugee setting is perilously swift; it is like throwing a lit match onto dry brush.

Measles is only one of many diseases preying on the people I see daily.

Meningitis season is just around the corner and already we are hearing reports of its arrival in Darfur.

Polio is re-emerging after a three-year absence in Sudan, according to new World Health Organisation data.

The water-borne disease usually infects young children by attacking the nervous system and causing paralysis, muscular atrophy, deformity and sometimes death.

Although previously eradicated in Darfur, polio is on the comeback because of the desperate conditions and lack of vaccination campaigns.

We are also mired in an outbreak of acute jaundice, called hepatitis E.

It has invaded the camps here, turning young eyes a bright neon yellow and making the weakest even weaker.

We spend our days like detectives, investigating the regions from which the hepatitis seems to spread.

With the right information and tools-such as chlorination, soap and plentiful latrines, we can halt the spread of this miserable epidemic, which has a 20% mortality rate among pregnant women.

Furtive, fast and formidable

We are already consumed with the ominous approach of cholera, which has already caused death and disability just across the border in Chad.

This army of bacteria is stealthily making its way to Darfur. These germs are furtive, fast and formidable.

Getting clean water is a major problem for Darfur's refugees

We are on the alert, gathering equipment and statistics to prevent disaster, tracking the flow of the cholera as it crosses the border into our regions.

We form our own armies and equip ourselves with fluids and rehydration salts and plastic sheeting.

We are ready for this enemy. But victory is not assured.

This, too, is the thick of malaria season, when the bite of a mosquito releases killer parasites into a waiting bloodstream. The parasites attack fragile red blood cells and without treatment, death may well result.

But, all is not lost; even the sickest patient can recover with the right treatment.

Just days ago, a young man arrived at our clinic on the back of a donkey-driven cart. He was feverish, delirious and surely near death.

But we at the clinic are as stubborn and persistent as the fiercest of bugs.

So we fight back.

Within hours, he was better; within days, he was back in his little hut in the camp, tired but alive.

We have learned to count our successes in small increments and small moments. For this man and his family, this triumph is sweet. This day, his joy is infinite and his thanks are immeasurable.